It is known to do PCR amplification and detection using a reaction vessel in which solid particles are fixed and liquid sample and reagents are moved sequentially past the fixed solid particles. Such reaction vessels are described, e.g., in EPA Publication 381,501. Although such vessels work well to confine amplified DNA from leaking out of the vessels and contaminating other test vessels, they do have a slight disadvantage--the liquid solutions must be carefully moved from place to place, without dislodging the fixed solid particles used for detection. As a result, the reaction vessel is carefully constructed in a way that excludes less expensive, simpler constructions. That is, liquid flow and attachment of the "fixed" solids must be maintained so that such solids do not migrate away from their read location.
Similarly, immunoassays are known in which a label reagent attached to a target bound to a solid (and called "bound" reagents) are separated from label reagents associated but unattached with the target (and called "free" reagents). This is done by fixing the solids in the test device and washing off the free reagent by flowing a wash liquid past or around the fixed solids. Typically a medium such as a solid filter is used to separate the bound reagents from the free reagents after the wash step. Examples are indicated in U.S. Pat. No. 4,921,677, which work well for their purpose. However, care is needed to select a filtering medium that, while passing free liquid, will not pass the solids bearings the bound reagent.
Thus, in both the PCR amplification and detection, and in the immunoassays noted above, the technique has been to fix or immobilize the solid particles, and to move the liquid.
There has been a need, therefore, prior to this invention, to provide a detection vessel and method, suitable for PCR amplification and detection while confined, or for immunoassay, that are less difficult to provide and/or less expensive than the currently available vessels and methods.
It was also known in the prior art to pour particulate solids bearing a target, such as for immunoassay, into a detection solution where unbound label reagent is washed off the solids as a bound-free separation. Examples can be found in, e.g., U.S. Pat. No. 4,743,536 to Evanega et al. However, invariably when such solids are poured or flowed into the detection solution, the chamber holding the solids is uncovered to allow the fluid flow. Such uncovering is totally unacceptable as a detection scheme for PCR since the containment needed in PCR amplification becomes lost. Because bulk flow of solids necessitates the opening of sizable channels between the respective compartments, the mere act of providing the bulk flow has in the past been counterproductive to maintaining confinement of PCR reaction products.
What has been desired, therefore, prior to this invention, is a method of flowing bulk solids between confined locations, namely from an amplifying location to a detecting location, without opening up the amplifying location to the atmosphere so as to cause contamination.